engleski

Stimulation of CD45RA^+ and CD45RC^+ cells in weaned pigs infected with enterotoxigenic Escherichia coli (ETEC) by oral immunization with non-ETEC strain

To investigate the influence of a live attenuated oral vaccine against porcine post-weaning colibacillosis (PWC) induced by enterotoxigenic Escherichia coli (ETEC) on intestinal lymphoid cell CD45 isoforms expression, experimental group of weaned pigs (n=6) was immunized orally with F4ac^+ non-ETEC strain (day 0) and challenged by F4ac^+ ETEC strain 7 days latter. Non-immunized ETEC-infected pigs (n=6) served as control. All pigs were killed on post-challenge day 7. The small intestine was excised for isolation of jejunal lamina propria (JLP) lymphocytes and immunohistochemical studies. The results obtained by immunophenotyping of isolated cells show that the proportion of CD45RA^+ and CD45RC^+ JLP cells increased in the experimental pigs vs controls. Additionally, while CD45RA^+ JLP cells increased only slightly, the expression of CD45RC isoform in the JLP cells was significantly higher (P<0.01) in the experimental than in the control group. The results of the quantitative phenotypic analysis of isolated lymphocytes were not confirmed by immunohistochemical in situ staining, since immunization with F4ac^+ non-ETEC failed to efficiently stimulate generation of CD45RC^+ T cells in the gut of the challenge-infected pigs. The majority of intestinal immune cells was found to express CD45RA antigen in situ, but no differences were observed between the two groups of weaned pigs neither in CD45RA^+ nor in CD45RC+ cells. Our overall evidence indicates that the increased expression of CD45RC isoform was in fact induced in a limited number of JLP T cells in the vaccinated pigs, casting F4ac^+ non-ETEC strain as low-specific immunogen. Its poor immunogenicity was indeed accompained with the impaired protection of weaned pigs from ETEC-induced PWC, suggesing that the disease might evolve, at least in part, as a consequence of inadequate activation of the CD45 isoforms in the gut mucosa of the pigs.

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